Needleless hypodermic injection system, application device and medication cartridge therefor

ABSTRACT

A needleless hypodermic injection system for injecting a liquid medication, which system comprises a disposable cartridge which contains a medication and which comprises a propellant and an igniter, and a reusable application device which comprises a pressure chamber for receiving the medication cartridge, actuation means including an ignition system and means for ensuring reliability and safety of the system. The reusable application device comprises: (a) a housing including a fist housing section and a second housing section which are adapted to be assembled together by a screwing operation, the first housing section comprising a front part having an injection outlet and a chamber adapted to receive a the cartridge contains the medication to be injected and also contains a propellant and an igniter, and (b) means for selectively activating said igniter of said cartridge when predetermined conditions are fulfilled.

PRIORITY TO RELATED APPLICATIONS

This application is a Continuation of Ser. No. 10/101,400, filed Mar.19, 2002 which is pending. This application claims the benefit of U.S.Provisional Application Ser. No. 60/278,042, filed Mar. 22, 2001.

FIELD OF THE INVENTION

The invention concerns a needleless hypodermic injection system forinjecting a liquid medication.

The invention also concerns a reusable application device which is afirst part of such a system.

The invention further concerns a disposable medication cartridge whichis a second part of such a system.

BACKGROUND OF THE INVENTION

Prior art systems and devices of the above mentioned kind have importantdisadvantages. They have a complex structure and are therefore not easyto assemble and to use, in particular for patients which have somehandicaps or are not in full possession of their handling capabilities.Moreover they lack reliable means for preventing accidental release ofinjections and their negative consequences, e.g. loss of expensivemedications and possible injures inflicted to the user.

The main aim of the instant invention is therefore to provide a systeman application device, and a medication cartridge of the above mentionedkind with which the above mentioned drawbacks can be eliminated or atleast substantially reduced.

SUMMARY OF THE INVENTION

According to a first aspect of the invention the above mentioned aim isattained with a needleless hypodermic injection system for injecting aliquid medication, which system comprises:

-   -   (a) a disposable cartridge which contains a medication and which        includes a propellant and an igniter, and    -   (b) a reusable application device which comprises a pressure        chamber for receiving said cartridge, and actuation means        including an ignition system and means for ensuring reliability        and safety of the system.

According to a second aspect of the invention the above mentioned aim isattained with a reusable application device for a needleless hypodermicinjection system for injecting a liquid medication contained in acartridge inserted into said application device, said application devicecomprising

-   -   (a) a housing including a first section and a second section        which are adapted to be connected with each other to form a        housing assembly,    -   said first housing section comprising a chamber for receiving a        cartridge containing a medication unit which contains a liquid        medication,    -   said first housing section having a symmetry axis which extends        along its length and a front part having an outer contact        surface which is adapted to be applied on a skin surface, said        contact surface having an opening through which liquid        medication ejected from said cartridge can pass and be injected        through said skin surface,    -   (b) ejection means for causing ejection of said liquid        medication contained in said cartridge in order to perform an        injection, a first part of said ejection means being contained        in said cartridge and a second part of said ejection means being        contained in said second housing section,    -   c) assembly detecting means which reach a first predetermined        state when said first housing section is properly and completely        assembled with said second housing section to form said housing        assembly, said assembly detecting means being located within        said housing assembly,    -   d) position detecting means which are located in part within        said first housing section and in part in said second housing        section, said position detecting means reaching a second        predetermined state when the following conditions are        simultaneously satisfied by the relative position of said        housing assembly with respect to said skin surface,    -   d.2) said contact surface of said first section exerts a        predetermined pressure on said skin surface, the distribution of        said pressure over the area of said contact surface being        substantially uniform, and    -   d.3) said symmetry axis of said first section is positioned        substantially normal to said skin surface, and    -   e) actuator means for activating said ejection means, said        actuator means being normally disabled and becoming operable        only upon being enabled by a combination of predetermined        effects provided by    -   said assembly detecting means after they reach said first        predetermined state, and    -   said position detecting means when they reach said second        predetermined state.

According to a third aspect of the invention the above mentioned aim isattained with a reusable application device for a needleless hypodermicinjection system for injecting a liquid medication contained in acartridge inserted into said application device, said cartridgecontaining a propellant adapted to be ignited by application ofelectrical energy to two electrical contacts which are part of saidcartridge, said application device comprising

-   -   a) a housing including a first section and a second section,        each of these sections having a length axis and said first and        second housing sections being adapted to be connected with each        other to form a housing assembly, said housing assembly being so        configured and dimensioned that it is adapted to be held by a        user with one hand,    -   b) said first housing section comprising a chamber for receiving        a cartridge containing a liquid medication, said first section        having an outer contact surface which is adapted to be applied        on a skin surface through which an injection is to be applied,    -   c) said second housing section containing electrical means for        causing ignition of a propellant contained in a cartridge        arranged in said chamber of said first housing section and        actuator means for activating said electrical means, and    -   d) position detecting means for detecting whether said contact        surface of said first section exerts a predetermined pressure on        said skin surface and whether at the same time said length axis        of said first section is positioned substantially normal to said        skin surface, the distribution of said pressure over the area of        said contact surface being substantially uniform, said means for        detecting enabling said actuator means when the latter        conditions are satisfied.

According to a fourth aspect of the invention the above mentioned aim isattained with a reusable application device for a needleless hypodermicinjection system for injecting a liquid medication, which applicationdevice comprises:

-   -   (a) a housing including a fist housing section and a second        housing section which are adapted to be assembled together by a        screwing operation,    -   said first housing section comprising a front part having an        injection outlet and a chamber adapted to receive a cartridge        containing a medication unit which contains the medication to be        injected, a propellant, and an igniter, and    -   (b) means for selectively activating said igniter of said        cartridge when predetermined conditions are fulfilled.

According to a fifth aspect of the invention the above mentioned aim isattained with a medication cartridge for a needleless hypodermicinjection system for injecting a liquid medication, said cartridgecomprising a housing adapted to contain:

-   -   (a) a first chamber containing a medication unit configured and        dimensioned to store a volume of liquid to be injected, said        medication unit having a first region and a second region that        are in liquid communication with each other, said first region        being deformable and said second region having an injection        outlet, and    -   (b) a second chamber containing a propellant,    -   said first chamber being divided by an elastic barrier in two        zones, a first zone containing said medication unit and a second        zone which is communication with said second chamber, so that        upon ignition of the propellant in the second chamber gas        generated thereby expands into said second zone of said first        chamber, exerts pressure on and deforms said barrier which in        turn transfers that pressure to and deforms said deformable        first region of said medication unit and thereby causes ejection        of said medication through said injection outlet, and    -   (c) means for mechanically setting the volume available within        said cartridge for gas said expansion, so that said volume has a        selected predetermined size.

The main advantages attained with the invention are as follows:

-   -   Injections can only be performed when plurality of predetermined        necessary conditions for a correct injection are satisfied.        Therefore, the risk of accidentally released injections and        their negative consequences, e.g. loss of expensive medications        and possible injure of user, are substantially reduced.    -   A device and a system according to the invention are easy, safe        and comfortable to use, so that they can be assembled and used        by patients or other persons without any training or special        instructions.    -   The manufacturing cost of a device and a system according to the        invention is not higher than prior art devices for the same        purpose.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject invention will now be described in terms of its preferredembodiments with reference to the accompanying drawings. Theseembodiments are set forth to aid the understanding of the invention, butare not to be construed as limiting.

FIG. 1 shows a schematic cross sectional view of a basic structure of amedication cartridge 11 used in a needleless injection system accordingto the invention.

FIG. 2 shows a schematic cross sectional view of the basic structure ofan application device according to the invention including arepresentation of a medication cartridge 11 according to FIG. 1.

FIG. 3 shows a schematic cross sectional view of the pressure chamberand locking means which are part of the application device according toFIG. 2 and which are adapted to enclose and contain a medicationcartridge 11 of the type shown by FIG. 1 during a high-pressureinjection.

FIG. 4 shows a schematic cross sectional view of a complete applicationdevice according to the invention without a medication cartridgeinserted thereinto.

FIG. 5 shows a side view of the nose section 42 of an application deviceof the kind shown by FIG. 4.

FIG. 6 shows a first perspective view of the nose section 42 shown byFIG. 5.

FIG. 7 shows a second perspective view of the nose section 42 shown byFIG. 5.

FIG. 8 shows a first exploded view of components of the nose section 42shown by FIGS. 5-7.

FIG. 9 shows a second exploded view of components of the nose section 42shown by FIGS. 5-7.

FIG. 10 shows a first schematic representation of the electricalignition circuit of an application device of the kind shown by FIG. 4.

FIG. 11 shows a second schematic representation of the electricalignition circuit of an application device of the kind shown by FIG. 4.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

According to the invention a reusable application device is used as partof a needleless hypodermic injection system for injecting a liquidmedication contained in a cartridge inserted into said applicationdevice.

Medication Cartridge Assembly

As shown by FIG. 1 a medication cartridge assembly 11 according to theinvention comprises components described hereinafter.

A cartridge shell 12 made e.g. of a plastic material contains amongother components a sealed medication module which comprises a nozzlebody 13 and a flexible container wall 14 that hermetically encloses aportion of the nozzle and forms a reservoir 15 for a liquid medication16 stored in the sealed medication module. This sealed module includingliquid medication 16 stored therein is manufactured under sterileconditions.

A part of the container wall 14 forms a break-off protective cap 17 thatcovers a jet orifice 18 of nozzle body 13. Cap 17 is removed by the userjust prior to use.

An envelope 21 made e.g. of rubber surrounds the flexible container wall14 and serves as a protective barrier. Envelope 21 protects flexiblewall 14 from direct hot gas contact, and prevents hot gas from enteringa fluid channel 22 within nozzle body 13 and jet orifice 18 of nozzlebody 13 even in the event of a break in the flexible container wall 14.Envelope 21 also forms a gas seal between the cartridge shell 12 and themedication module containing the liquid medication 16.

Cartridge shell 12 unifies the components contained therein and containsalso gas generated within cartridge shell 12 by a gas generatorcontained therein during actuation. The wall of cartridge shell 12 maybe relatively thin since it transfers the gas pressure forces generatedwithin cartridge shell 12 to a surrounding high strength chamber that ispart of a reusable actuation device described hereinafter.

Injection energy is provided by a gas generator located in the rear partof cartridge shell 12. This gas generator is a subassembly consisting ofa metal gas generator body 23 which has a propellant containing chamber24 located between an outlet orifice plate 25 and a closure plug orclosure plate 26. When the gas generator is actuated in order to providethe energy necessary for performing an injection of the liquidmedication, a propellant contained in propellant chamber 24 is ignitedby an electrically heated wire and produces hot gas that flows to gaspressure chamber 27 surrounding envelope 21, flexible container wall 14and medication reservoir 15 and an annular co-volume 28 the size ofwhich is defined by the axial position of a co-volume seal ring 34.

Heating wire adapted to be electrically heated is arranged withinpropellant chamber 24. This heating wire is electrically connected withignition contacts 31, 32 arranged in closure plate. When the medicationcartridge assembly is properly positioned within the reusableapplication device ignition contacts 31, 32 engage correspondingelectrical contacts which are part of the application device describedhereinafter. Electric power is deliverable to the heating wire 35 (shownin FIG. 11) arranged within propellant chamber 24 through the lattercontacts and ignition contacts 31, 32 engaged therewith.

Cartridge shell 12 further contains an internal support 33 which e.g. astructure made of a plastic material that snaps into cartridge shell 12and holds the above described sealed medication module and the gasgenerator in position. When cartridge assembly 11 is inserted into andproperly positioned within an application device described hereinafterin order to perform an injection, a part of this application devicepushes on the rear of cartridge assembly 11 and clamps the closure plate26 of the gas generator, internal support 33, envelope 21 and the abovedescribed sealed medication module into the nose of cartridge shell 12.Cartridge assembly 11 remains so clamped during actuation thereof by theapplication device for performing the injection. This clamping action oncartridge assembly 11 assures that this assembly is hermetically sealedto prevent hot gas leakage around jet orifice 18 of nozzle body 13.

When a cartridge assembly is actuated by the application device,pressure exerted by gas surrounding a part of the sealed medicationmodule within cartridge shell 12 is transmitted to liquid medication 16contained in the sealed medication module through flexible containerwall 14. The pressure exerted in this way on the liquid medicationcauses a collapsing of flexible container wall 14 and this drives theliquid medication through jet orifice 18 at high velocity. Peakpressure, up to 300 bar, occurs at the beginning of the injection andforces a jet of liquid medication to penetrate through a skin layer andthereby form a fluid delivery channel into the subcutaneous tissue. Thepressure then drops to about 100 bar to complete the medicationinjection through the so formed fluid delivery channel.

Ease of jet penetration varies between patients or between injectionsites on the same patient. The initial peak injection pressure istherefore adjusted to control the jet penetration force to anappropriate value. This adjustment is effected by positioning co-volumeseal ring 34 at a suitable axial position with respect to cartridgeshell 12 in order to set the value of the annular co-volume 28.

Increasing co-volume 28 increases the expansion volume of the gasgenerated and delivered by the gas generator and reduces the initialpeak pressure to a lower value. A co-volume setting ring 48 that is partof the application device described hereinafter slides into the rear ofcartridge 11 during loading of cartridge 11 into the application device,brings co-volume seal ring 34 into a selected position and holds thisring in this position.

A cartridge assembly 11 clamped into the actuation device describedhereinafter is a hermetically sealed assembly, and retains as much as100 bars pressure after actuation. The application device must thereforerelease the clamping force in a controlled way and allow that the gaspressure within cartridge 11 forces closure plug 26 of the gas generatorout to break the seal with the gas generator body 23 and vent the gas.This controlled pressure release makes it easy to open the applicationdevice after it is used to perform an injection and prevents that theamount of pressure remaining in the cartridge after an injection maycause an undesirable forceful opening of the application device that maycause an injury to a user of the device.

Structure of an Application Device According to the Invention

The above described characteristics of cartridge assembly 11 define thebasic functional requirements the application device has to satisfy.Additional requirements ensure safe and easy operation of theapplication device.

The force a user has to apply for loading a cartridge 11 into anapplication device and the force a user has to apply for removing acartridge 11 from the application device after use for performing aninjection must be low enough to allow easy and sure operation of theapplication device by ill or elderly patients.

Actuation of the application device must not be possible unless thedevice is fully closed and locked. Otherwise partial engagement of thelocking mechanism might lead to failure and possible injury caused bythe high pressure created during an injection operation.

To ensure that actuation of the application device is not possibleunless the device is fully closed and locked, operation of anapplication device according to the invention requires that the nosepart of the application device is pressed uniformly and with apredetermined force against the skin surface to be injected beforeactuation of the application device is enabled. Main objectives of thissecurity measure are to prevent accidental actuation resulting inejection of a liquid jet that might cause eye injury and also to preventwasted injections due to premature actuation of the application devicebefore the nose part thereof is properly pressed against the skinsurface at the injection site.

The outer surface of the application device should not have any sharpedges or pinch points and the design of the application device has tosatisfy ergonomic requirements.

The shape of the application device has to be well adapted to thefunction it has to perform and therefore the procedures for loading andunloading a cartridge 11 into the application device and for actuatingthe application device should be so obviously and intuitively clear tothe user that a minimum of user instruction is necessary to ensureproper use of the application device.

Moreover, the application device and in particular the area around thecartridge nozzle that contacts the skin during the injection should beadapted to be easily cleaned.

The injection system formed by cartridge 11 and the application devicedescribed hereinafter should be fail-safe and resistant to tampering.Any faults in the device should result in failure of device actuationrather than in an unexpected or dangerous actuation. The design of thelatter injection system should be such that it discourages a “clever”person from modifying or tricking the device so that it operatesimproperly.

The application device described hereinafter meets the requirementsoutlined above.

As shown by FIG. 2, an application device 41 according to the inventioncomprises two sections: a nose section 42 which comprises a pressurechamber 49 defined by the interior of a shell 43 and adapted forreceiving a cartridge assembly 11, and a base section 44 which comprisesamong other components a breech block 45 and an electrical ignitionsystem (not shown in FIG. 2).

Nose section 42 and a base section 44 are assembled in two steps. In afirst step a cartridge 11 is inserted into pressure chamber 49 of nosesection 42 and after that nose section 42 and the cartridge 11 insertedthereinto are mechanically connected to base section 44. For thispurpose, nose section 42 and base section 44 are twisted with respect toeach other ¼ turn to provide engagement of a set of locking lugs.

In a second step nose section 42 is twisted of about one turn withrespect to base section 44 for tightening a screw mechanism that clampscartridge assembly 11 with a required preload of e.g. 200 Newton. Atthis point application device 41 is ready for performing an injection.For this purpose, the user removes break-off protective cap 17 fromcartridge 11, presses jet orifice 18 of nozzle body 13 against a skinsurface at the injection site, and then presses an actuation switch torelease an injection.

Interlocks prevent actuation of the application device if it is notfully closed and if the skin contact surface of its nose section 42 isnot uniformly pressed against the skin surface.

A spent cartridge is removed by reversing the loading process. For thispurpose, nose section 42 is twisted of about one turn with respect tobase section 44 to release the clamp screw mechanism and vent theresidual cartridge gas pressure. The locking lugs are then disengaged bya further ¼ turn, and nose section 42 and base section 44 are separatedfrom each other so that the spent cartridge may be removed anddiscarded.

Application device 41 is a tightly integrated system that comprises thefollowing subsystems:

Pressure Chamber and Lock

Pressure chamber 49 and a lock which includes the above mentioned breechblock are a set of mechanical components that enclose and contain acartridge assembly 11 during a high-pressure injection.

Housing

A housing encloses and supports the other subsystems which form part ofan application device according to the invention. This housing alsoforms the surfaces the user grips to administer injections and to openand close the application device for loading, respectively unloading ofa cartridge 11.

Electric Ignition System

An electric ignition system includes a battery, an actuation switch,safety interlock switches and electrical connection leads. Theelectrical ignition system supplies electric current to the ignitioncontacts 31, 32 of cartridge 11 and thereby to ignition wire 35 (seeFIG. 11) to start an injection process when the user presses theactuation switch.

Object Sensor

An object sensor comprises a mechanical structure surrounding jetorifice 18 of nozzle body 13 of cartridge 11. This mechanical structurecomprises a skin contact surface of nose section 42. Two diametricallyopposite places of this skin contact surface must be pressed against theinjection site in order to enable application device 41 to actuate acartridge 11 which has been loaded into application device 41.

The following sections describe each of the above mentioned subsystemsin detail.

Pressure Chamber and Lock Mechanism

FIG. 3 shows a general arrangement of a pressure chamber 49 and a lockmechanism 51. Pressure chamber 49 is the interior of a generallycylindrical shell 43 with a reduced diameter opening 46 at one end and afull diameter opening 47 at the other end. The shell 43 of pressurechamber 49 is manufactured from high strength steel and dimensioned suchthat it will withstand about 900 bar internal pressure (that is threetimes a 300 bar maximum working pressure) without damage.

Lock mechanism 51 is part of a mechanical structure contained in andcarried by base section 44. In order to load a new cartridge into theapplication device or to unload an spent cartridge from the applicationdevice, nose section 42 and base section 44 are disassembled asdescribed above in order to separate the shell 43 of pressure chamber 49from lock mechanism 51.

When cartridge 11 is inserted into pressure chamber 49 break-offprotective cap 17 and the outer end of nozzle body 13 extend through thereduced diameter opening 46 of the shell 43 of pressure chamber 49. Theshell 43 of pressure chamber 49 has a clearance fit with respect tocartridge shell 12. During an injection process the internal pressurewithin cartridge shell 12 expands it elastically and its outer wallcontacts the internal surface of the shell 43 of pressure chamber 49,thereby transfers the pressure load to the shell 43 of pressure chamber49 during the injection process, and limits the mechanical stress oncartridge shell 12. After an injection, the residual pressure incartridge shell is released by venting (as described above) andcartridge shell elastically contracts. This restores the clearance fitof cartridge shell 12 with respect to the shell 43 of pressure chamber49 and this allows easy removal of a used cartridge. Nozzle body 13 ofcartridge 11 has sufficient strength to bridge the reduced diameteropening 46 and withstand the internal pressure in cartridge 11 during aninjection process.

Full diameter opening 47 of the shell 43 of pressure chamber 49 isclosed when shell 43 is engaged with lock mechanism 51. Lock mechanism51 has several functions. A first function of lock mechanism 51 is thatit locks to the shell 43 of pressure chamber 49 and carries the axialpressure force (which is a function of the cartridge internal diameterand the gas pressure) which tends to separate lock mechanism 51 from theshell 43 of pressure chamber 49. A second function of lock mechanism 51is that it carries the ignition contacts of the application device thatengage the ignition contacts 31, 32 of cartridge 11. A third function oflock mechanism 51 is that it carries an interchangeable co-volumesetting ring which serves for setting the axial position of theco-volume seal ring 34 in cartridge 11. A fourth function of lockmechanism 51 is that it comprises a clamp screw 52 that allows the userto apply the necessary clamping force on cartridge 11 prior to actuationthereof, and to release the residual pressure in cartridge 11 in a slowand controlled way after an injection process. A fifth function of lockmechanism 51 is that it contains a mechanical interlock that assuresthat locking lugs are fully engaged before clamp screw 52 can be turnedto prepare and bring the system composed by the application device andcartridge 11 to a state that allows actuation of cartridge 11 by theapplication device. Each of these functions is described in more detailin the following sections.

A pair of male locking lugs 53 on the shell 43 of pressure chamber 49engage female pockets 54 in a receiver ring 55 of lock mechanism 51 toform a structural connection. The user makes this connection byinserting locking lugs 53 into receiver ring 55 with an axial motion,and then rotating the shell 43 of pressure chamber 49 ¼ turn withrespect to receiver ring 55 to engage locking lugs 53 with femalepockets 54. This type of connection is widely used in firearms and hosecouplings because of its strength and reliability.

After locking lugs 53 are fully engaged with female pockets 54, clampscrew 52 is turned to push breechblock 45 into cartridge 11. Clamp screw52, the shell 43 of pressure chamber 49, receiver ring 55 andbreechblock 45 are all on a common axis, i.e. they are coaxiallyarranged. This screw action preloads the sealing of cartridge 11 with aforce of about 200 Newtons, sets the axial position of co-volume sealring 34 to a selected position, and pushes the ignition contacts of theapplication device against the ignition contacts of cartridge 11 so thatelectrical contact is established between these ignition contacts.

After an injection process is terminated, a 100 bar residual pressure incartridge 11 generates a force of about 1600 Newtons on clamp screw 52.Under this mechanical load, the user turns clamp screw 52 to retractbreechblock 45 and vent cartridge 11. One of the ends of clamp screw 52has right hand threads that engage matching threads in receiver ring 55,whereas the opposite end of clamp screw 52 has left hand threads thatengage matching threads in breechblock 45. One or more pins in receiverring 55 engage matching axial slots in breechblock 45, and preventrotation of breechblock 45 while allowing axial motion thereof. Theprovision of clamp screw 52 with the above mentioned different threadsmakes it possible to obtain an axial displacement of breechblock 45 perrevolution of clamp screw 52 that is twice as long as the axialdisplacement that would be obtained if clamp screw 52 had only a singletype of thread with the same thread pitch distance. A suitable choice ofthread diameter and pitch favorably influences the amount of effortneeded for disassembling, respectively assembling application device 41.This is discussed in more detail hereinafter.

A pair of interlock levers 56, 57 consisting each of a latch portion 69and an arm portion 68 are pivot mounted on a pivot 70 to the receiverring 55. Interlock levers 56, 57 lie in a plane that includes thesymmetry axis of receiver ring 55, and the pivot axes are perpendicularto this plane and symmetrically placed on each side of the symmetry axisof the receiver ring. Interlock levers 56, 57 are spring biased by abias spring 60 so that the latch portions 69 engage a pair of grooves(not shown) in clamp screw 52, preventing screw rotation. When the shell43 of pressure chamber 49 is inserted into receiver ring 55, the armportions 68 of interlock levers 56, 57 slip into a pair of cam grooves58, 59 in the shell 43 of pressure chamber 49. Cam grooves 58, 59 areshaped to move the arm portions 68 of interlock levers 56, 57 as theshell 43 of pressure chamber 49 is rotated to engage locking lugs 53, sothat the latch portions 69 are removed from the clamp screw grooves. Theresult is that rotation of clamp screw 52 is only possible when thelocking lugs 53 are fully engaged with pockets 54.

A second function of interlock levers 56, 57 is to prevent rotation oflugs 53 and disengagement thereof from pockets 54 once clamp screw 52 isrotated from the starting position to clamp cartridge 11 and thereby theclosure plug of cartridge 11 and pressure chamber 49 by means ofbreechblock 45. When clamp screw 52 is rotated, the latch portions 69 ofthe interlock levers 56, 57 ride on the outside diameter of clamp screw52, and can no longer enter the clamp screw grooves and rotate aboutpivots 70. The arm portions 68 of interlock levers 56, 57 are thereforeimmovable, and bear against the sides of the cam grooves 58, 59 in theshell 43 of pressure chamber 49 and block rotation of locking lugs 53.This ensures that lugs 53 remain fully engaged with pockets 54 duringactuation of cartridge 11 and can only be disengaged after clamp screw52 is returned to the starting position. At this point the latchportions 69 of interlock levers 56, 57 can again drop into the clampscrew grooves, allowing the latches 69 of interlock levers 56, 57 torotate about the pivots 70.

A third function of interlock levers 56, 57 is to prevent shell 43 ofpressure chamber 49 from being inserted if clamp screw 52 is not in thestarting position. In this condition the latch portions 69 of theinterlock levers 56, 57 ride on the outside diameter of clamp screw 52,displacing the arm portions 68 of the levers so that they do not enterthe cam grooves in the shell 43 of pressure chamber 49. This blocks theshell 43 of pressure chamber 49 from entering the receiver ring 55 farenough for the locking lugs 53 to engage pockets 54. The situation inwhich the shell 43 of pressure chamber 49 is removed and the clamp screw52 is not in the starting condition is not normal, and indicates damageor tampering. Correction of this anomalous state requires device serviceor replacement.

By careful selection of the design parameters of clamp screw 52, therequired effort to assembly and disassembly application device 41 areapproximately equal and this results in greatly improved ease of use.

Frictional torque of clamp screw 52 varies in function of axial load,screw thread diameter, and friction coefficient. Load reaction torquevaries in function of axial load and thread pitch. The reaction torqueadds to the friction torque in the closing direction (when assemblingapplication device 41), and increases the user effort. Conversely, thereaction torque subtracts from the friction torque in the openingdirection (when disassembling application device 41) and assists theuser. Since the axial force is about 200 Newtons in the closingdirection and about 1600 Newtons in the opening direction, according tothe invention the parameters of clamp screw 52 are selected to equalizethe opening and closing torque. The following table summarizes theresults of a typical design calculation. Parameter Value Clamp screwdiameter 8 mm Screw thread friction coefficient 0.12 Peak closing force200 N Peak opening force 1600 N Equalized opening and closing torque 20N-cm Screw pitch (Total of left and right 6 mm hand clamp screwsections)Housing

FIG. 4 shows a cross section of application device 41 including thehousing components. As well as containing the functional components, thehousing has important functions of its own. The nose section 42 of thehousing is rigidly connected to the shell 43 of pressure chamber 49, andserves as one handle through which the user applies opening and closingtorque. The base section 44 of the housing is rigidly connected to clampscrew 52, and serves as the other handle. The base section 44 of thehousing rotates relative to the receiver ring 55 and breechblock 45. Incombination, the nose section 42 and the base section 44 of the housingalso act as visual and tactile indicators, since they have oval profilesthat line up when the device is fully closed. Closure of applicationdevice 41 is assisted by a spring-loaded pin and detent 61 that latchthe application device 41 in the closed position. Additional functionsand features of the housing will become evident in the descriptions ofother aspects of application device 41.

FIGS. 5 to 9 show various views of the nose section 42 and of some ofits components. FIG. 5 shows a side view of the nose section 42 of anapplication device of the kind shown by FIG. 4. FIG. 6 shows a firstperspective view of the nose section 42 shown by FIG. 5. FIG. 7 shows asecond perspective view of the nose section 42 shown by FIG. 5. FIG. 8shows a first exploded view of components of the nose section 42 shownby FIGS. 5-7. FIG. 9 shows a second exploded view of components of thenose section 42 shown by FIGS. 5-7.

Electric Ignition System

FIGS. 10 and 11 show schematic representations of the electric ignitionsystem of application device 41.

In its simplest form, the electric ignition system of application device41 consists of a battery 62, an actuation switch 63 controlled by theuser, electrical contacts that engage electrical contacts of cartridge11, and interconnection conductors. The user loads a fresh cartridge 11into application device 41, closes and locks this device, removesbreak-off protective cap 17, presses jet orifice 18 against the skin atthe injection site, and then presses push button 63 of the actuationswitch. Current passing through an electrically heated wire in the gasgenerator of cartridge 11 lights the propellant and starts theinjection. The invention uses this basic approach, and adds interlockmechanisms to reduce the chance of premature actuation that could causea hazard or waste an injection cartridge.

The physical configuration of the electric ignition system of thisinvention is illustrated in FIG. 4. Except as noted, the ignitioncomponents are attached to the base section 44 of the housing. Battery62 is permanently connected by soldering or a similar means, and willnormally last the life of application device 41. The positive batteryterminal 64 is electrically connected to the input terminal of thenormally open actuation microswitch 71, and the negative terminal 65 isconnected to the input terminal of the normally open interlockmicroswitch 72. The output terminal of the actuation microswitch 71 isconnected to a conductive spring member 73 that is biased into contactwith the central ignition contact pin 66. This contact connection isrequired since the central ignition contact pin 66 rotates with thereceiver ring 55, not with the base section 44 of the housing. Theoutput terminal of the interlock microswitch 72 is connected to aconductive spring member 67 that is biased into contact with the slidingconductive transfer pin 74 in the receiver ring 55. The transfer pin 74forms a conductive path from the conductive spring member 67 to theco-volume setting ring 48 and then to the breechblock 45. Because thebase section 44 of the housing and the receiver ring 55 have rotationaland axial relative motion, contact takes place and ignition is possibleonly when clamp screw 52 is in the predetermined actuation position.

The central ignition contact pin 66 presses against the cartridge centerignition contact 32. The pin head 75 is structurally connected to thesliding breechblock 45, but electrically isolated by an insulatingbushing 76. The pin shaft passes through clearance holes in thebreechblock 45 and clamp screw 52, and is supported on center by aninsulating sleeve bearing 77 to maintain electrical isolation.

The electrically conductive sliding breechblock 45 presses against theouter ignition contact 31 of cartridge 11. As described above, currentcan only flow to the breechblock 45 when the clamp screw 52 is in theactuation position and the transfer pin 74 makes contact with theconductive spring member 67.

When the interlock microswitch 72 is closed and the clamp screw 52 is inthe actuation position, the actuation microswitch 71 is the onlyremaining barrier to current flow through the ignition contacts and theelectrically heated wire 35 in cartridge 11. This results in the batteryvoltage appearing between the input and outlet terminals of theactuation microswitch 71. This “ready to actuate” condition is visuallyindicated by a LED 78 connected across the terminals. Actuation thentakes place when the user closes the actuation microswitch 71 bypressing push button 63.

A mechanism consisting of a pushbutton 63, coil spring 81, pin lever 82and flat spring 83 is used to close the actuation microswitch 71 whenthe user presses the push button 63. This arrangement allows thepushbutton 63 to be positioned so that it is convenient for the user,while the actuation microswitch 71 is positioned where housing space isavailable. The pushbutton 63 slides in a sleeve 84 in the housing, andis biased out by the coil spring 81. The pin lever 82 serves a dualpurpose. First, it is pressed into the pushbutton 63 and extends intoopenings in the sides of the sleeve 84 to retain the pushbutton 63 inthe housing. Second, it acts as a lever that transfers the pushbuttonmotion to the flat spring 83 that engages the actuation microswitchoperating plunger 85. The pin lever 82 pivots in a hole in the side ofthe sleeve 84 nearest the nose section 42 of the housing of theapplication device 41, and swings through a slot 86 in the oppositeside. The flat spring 83 is anchored at one end, and passes over themicroswitch 71 and extends to engage the end of the pin lever 82. Whenthe pin lever 82 swings, it deflects the flat spring 83 towards theactuation microswitch 71 and pushes the actuation plunger 85. The sleeve84 in the housing is made of translucent plastic that is illuminated bythe “ready to actuate” LED 78.

The schematic representation of the electrical ignition system shown byFIG. 10 illustrates the fact that in order that an injection can beperformed with application device 41 the following switches have to beclosed: switches 71, 72, and switch formed by lock mechanism 51,spring-loaded pin and detent 61 and electrical conductive transfer pin74. This latter switch is only then closed when the application device41 is completely assembled, that is when the components contained innose section 42, in base section 44, and the cartridge 11 are all in theproper position with respect to each other.

The schematic representation of the electrical ignition system shown byFIG. 11 illustrates the state of this system when the application device41 is completely assembled and all necessary contacts for the ignitionare established with exception of switches 71 and 72 which are stillopen. In this state LED 78 received a current limited by resistor 79.This current is well below the value necessary to cause ignition byelectrically heating ignition wire 35, but is large enough to causelight emission by LED 78 and thereby signalize that application device41 would become ready for performing an injection if and when properlypositioned on the injection site.

When the application device 41 reaches a proper position on theinjection site, switch 72 is closed by this positioning, and actuationof push button 63 by the user can then cause closure of switch 71. Ifthis happens, the electrical ignition circuit is closed and asufficiently large current is fed to ignition wire 35 to cause ignitionof the propellant in cartridge 11.

Object Sensor/Position Detector

The object sensor or position detector requires the nose section 42 ofthe housing of the application device 41 to be pressed uniformly againstthe skin surface at the injection site before actuation ispossible/allowed. The object sensor/position detector is illustrated inFIG. 4. The nose section 42 of the housing includes a flat annularsurface 91 which surrounds the end of the shell 43 of pressure chamber49 that protrudes from the housing and the injection nozzle. A pair ofdiametrically opposed sensor pins 92, 93 slide in holes in the housing,and their ends extend a short distance above the surface in the restposition. The interlock system according to the invention requires thatboth sensor pins 92, 93 are pushed flush with the annular surface 91 toenable execution of an injection. Sensor pins 92, 93 support aconcentric rigid metal sensor ring 94 that is free to pivot at thecontact points with the sensor pins 92, 93. This defines the conditionthat two or more separate points must be pressed to push the sensor ring94 and both pins 92, 93 flush with the annular surface 91 and enableexecution of an injection. If the sensor ring 94 is pressed at any onepoint around its circumference it will tip, and at most one of the twosensor pins 92, 93 will be pushed flush with the annular surface 91. Theannular area, including the sensor ring 94 and sensor pins 92, 93, iscovered by a flexible rubber boot 95. The inner edge of the boot 95 isbonded to the shell 43 of the pressure chamber 49 at a bond point 105,and the outer edge of boot 95 fits in a groove in the nose section 42 ofthe housing. The boot 95 forms a smooth, easily cleaned surface andprotects the mechanism. It also retains the sensor ring 94 and holds itin the proper spatial relationship with the sensor pins 92, 93 at therest position.

The sensor pins 92, 93 push a relay ring 96 inside the nose section 42of the housing. The relay ring 96 in turn pushes a tilt plate 97. Thetilt plate 97 contacts the relay ring 96 with two diametrically opposedraised pivot points 98 (98 a respectively 98 b), and two diametricallyopposed legs 99 (99 a respectively 99 b) extend towards the base section44 of the housing. The legs 99 are offset 90 degrees from the pivotpoints 98, and lie in the same plane as the sensor pins 92, 93. A returnspring 101 formed from sheet spring material pushes the tilt plate 97,relay ring 96 and sensor pins 92, 93 towards the nose section 42 of thehousing so that the sensor ring 94 is pushed out to the rest position. Acover plate 102 on the surface of the nose section 42 of the housingthat abuts the base section 44 of the housing supports the return spring101 and shields the mechanism. The tilt plate legs 99 pass through holesin the cover plate 102, with their ends flush with the outer surface inthe rest position.

When the nose section 42 of the housing is attached to the base section44 of the housing and the clamp screw 52 is locked, one of the two tiltplate legs 99 is aligned with the interlock push pin 103. This pincontacts the interlock microswitch plunger 104, and closes the interlockmicroswitch 72 when it is pushed by one of the tilt plate legs 99. Theother tilt plate leg contacts the base section 44 of the housing andforms a pivot point. If the sensor ring 94 pushes both sensor pinsfully, then the relay ring 96 is pushed uniformly against the two tiltplate pivot points. This causes the tilt plate 97 to rotate around thepivot point formed by the leg in contact with the housing so that theother leg extends, pushes the interlock push pin 103, and closes theinterlock microswitch 72. In the event that only one sensor pin 92 or 93is pushed, the relay ring 96 tilts rather than moving uniformly. The twopoints on the relay ring 96 that contact the tilt plate 97 pivots moveonly half the full distance, with the result that the tilt plate leg 99moves only half the full distance and does not close the interlockswitch 72.

This above described object sensor/position detector has a number ofuseful features. First, it is electromechanical, and does not containany electronic devices that are sensitive to and whose operation can beaffected by spurious signals from electrostatic discharge or othersources of electromagnetic interference. Second, the electric ignitioncircuit is totally within the base section 44 of the housing, with noconnections to the removable nose section 42 of the housing that couldcompromise reliability. Third, additional safety is provided by the factthat the device must be fully closed and locked to align the tilt plateleg 99 with the interlock push pin 103. Fourth, the structure of theobject sensor/position detector is symmetrical, so that the nose section42 of the housing may be connected to the base section 44 of the housingin either of two positions which are angularly spaced from each other of180 degrees.

List of Reference Numbers

-   11 medication cartridge/cartridge assembly-   12 cartridge shell-   13 nozzle body-   14 flexible container wall-   15 medication reservoir-   16 liquid medication-   17 break-off protective cap-   18 jet orifice-   19-   20-   21 envelope-   22 fluid channel-   23 gas generator body-   24 propellant chamber-   25 outlet orifice plate-   26 closure plug/closure plate-   27 gas pressure chamber-   28 annular co-volume-   29-   30-   31 ignition contact-   32 ignition contact-   33 internal support-   34 co-volume seal ring-   35 electrically heated wire/ignition wire-   36-   37-   38-   39-   40-   41 application device-   42 nose section-   43 shell of pressure chamber-   44 base section-   45 breech block-   46 reduced diameter opening-   47 full diameter opening-   48 co-volume setting ring-   40 pressure chamber-   50-   51 lock mechanism-   52 clamp screw-   53 male locking lugs-   54 female pockets-   55 receiver ring-   56 interlock lever-   57 interlock lever-   58 cam groove-   59 cam groove-   60 bias spring-   61 spring-loaded pin and detent-   62 battery-   63 push button/actuation button-   64 positive terminal-   65 negative terminal-   66 central ignition contact pin-   67 conductive spring member-   68 arm portion-   69 latch portion-   70 pivot-   71 actuation micro-switch-   72 interlock micro-switch-   73 electrical conductive spring member-   74 electrical conductive transfer pin-   75 pin head-   76 insulating bushing-   77 insulating sleeve bearing-   78 Light Emitting Diode (LED)-   79 electrical resistance-   80-   81 coil spring-   82 pin lever-   83 flat spring-   84 sleeve-   85 operating plunger/actuation plunger-   86 slot-   87-   88-   89-   90-   91 flat annular surface-   92 sensor pin-   93 sensor pin-   94 metal sensor ring-   95 flexible rubber boot-   96 relay ring-   97 tilt plate-   98 pivot point (98 a, 98 b)-   99 leg (99 a, 99 b)-   100-   101 return spring-   102 cover plate-   103 interlock push pin-   104 interlock microswitch plunger-   105 bond point

Although a preferred embodiment of the invention has been describedusing specific terms, such description is for illustrative purposesonly, and it is to be understood that changes and variations may be madewithout departing from the spirit or scope of the following claims.

1. An application device for needleless hypodermic injection of a liquidmedication said application device comprising a) a housing having alength axis and an outer contact surface which is adapted to be appliedon a skin surface through which an injection is to be applied; b) saidhousing containing ejection means causing ejection of said liquidmedication in order to perform an injection and actuator means foractivating said ejection means; and c) position detecting means fordetecting whether said contact surface of said housing exerts apredetermined pressure on said skin surface and whether at the same timesaid length axis of said housing is positioned substantially normal tosaid skin surface, the distribution of said pressure over the area ofsaid contact surface being substantially uniform, said means fordetecting enabling said actuator means when the latter conditions aresatisfied.
 2. A device according to claim 1, wherein the ejection meanscomprise a propellant and means for its ignition.
 3. A device accordingto claim 1, wherein said position detecting means exclusively comprisemechanical and electro-mechanical means, but no electronic meanssensitive to electrical noise or other perturbating electrical signals.4. A device according to claim 1, wherein said position detecting meanscomprise a first switch adapted to be mechanically actuated by a movablepart of said position detecting means to establish an electricalconnection when said position detecting means senses application of thecontact surface of the housing on said skin surface with a predeterminedpressure applied on the skin surface.
 5. A device according to claim 1,wherein said housing is so configured and dimensioned that it is adaptedto be held and used by a user with only one hand.
 6. A device accordingto claim 1, further comprising means providing a visual or audibleindication to the user when said actuator means is enabled.
 7. A deviceaccording to claim 1, wherein the position detecting means comprise apurely mechanical object sensor, and a first switch adapted to bemechanically actuated by a movable part of the position detecting meansto establish an electrical connection when said object sensor sensesapplication of the contact surface of the housing on a body part.
 8. Areusable application device for needleless hypodermic injection of aliquid medication said application device comprising a) a housing havinga length axis and an outer contact surface which is adapted to beapplied on a skin surface through which an injection is to be appliedwherein the housing comprises a first section and a second section whichare adapted to be connected with each other to form a housing assembly,said first housing section comprising a chamber for receiving acartridge containing a medication unit which contains a liquidmedication, said first housing section having a symmetry axis whichextends along its length and a front part having the outer contactsurface which is adapted to be applied on a skin surface, said contactsurface having an opening through which liquid medication ejected fromsaid cartridge can pass and be injected through said skin surface; b)said housing containing ejection means causing ejection of said liquidmedication in order to perform an injection and actuator means foractivating said ejection means wherein a first part of the ejectionmeans is contained in said cartridge and a second part of said ejectionmeans is contained in said second housing section; c) assembly detectingmeans which reach a first predetermined state when said first housingsection is properly and completely assembled with said second housingsection to form said housing assembly, said assembly detecting meansbeing located within said housing assembly; d) position detecting meansfor detecting whether said contact surface of said housing exerts apredetermined pressure on said skin surface and whether at the same timesaid length axis of said housing is positioned substantially normal tosaid skin surface, the distribution of aid pressure overt the area ofsaid contact surface being substantially uniform, said means fordetecting enabling said actuator means when the latter conditions aresatisfied wherein the position detecting means are located in partwithin said first housing section and in part in said section housingsection, said position detecting means reaching a second predeterminedstate when the following conditions are simultaneously satisfied by therelative position of said housing assembly with respect to said skinsurface, d.2) said contact surface of said first section exerts apredetermined pressure on said skin surface, the distribution of saidpressure over the area of said contact surface being substantiallyuniform, and d.3) said symmetry axis of said first section is positionedsubstantially normal to said skin surface; and e) the actuator means arenormally disabled and become operable only upon being enabled by acombination of predetermined effects provided by said assembly detectingmeans after they reach said first predetermined state, and said positiondetecting means when they reach said second predetermined state.
 9. Adevice according to claim 8, wherein said second housing sectioncomprises means which are adapted to cooperate with a corresponding partof said first housing section for clamping with a predetermined preloadand for hermetically closing a cartridge inserted into said cartridgereceiving chamber.
 10. A device according to claim 8, wherein said firsthousing section and said second housing section are so shaped,dimensioned and configured that proper and complete assembly thereforeis accurately defined and recognizable by visual and tactile inspection.11. A device according to claim 8, wherein said first housing sectionand said second housing section are adapted to be assembled together byassembling steps which include a screwing operation.
 12. A deviceaccording to claim 8, wherein injection is caused by an electricalcircuit comprising a battery, a first switch a second switch adapted tobe actuated by a user, interconnection conductors, and two electricalterminals which correspond to respective terminals of an igniter, saidelectrical circuit being so configured that electrical current can flowfrom the battery to the igniter only when the following conditions aremet: i) said cartridge is properly positioned within said chamber ofsaid first housing section. ii) said first and said second housingsection are completely and properly assembled, whereby said twoterminals of said electrical circuit contact said respective terminalsof said igniter. iii) said first switch is actuated by said objectsensor and thereby establishes an electrical connection, and iv) saidsecond switch is actuated by a user.
 13. A device according to claim 8,wherein said assembly detecting means exclusively comprise mechanicalmeans.
 14. A needleless hypodermic injection system for injecting aliquid medication, which system comprises: a) an application deviceaccording to claim 1 i) a housing having a length axis and an outercontact surface which is adapted to be applied on a skin surface throughwhich an injection is to be applied; ii) said housing containingejection means causing ejection of said liquid medication in order toperform an injection and actuator means for activating said ejectionmeans; and iii) position detecting means for detecting whether saidcontact surface of said housing exerts a predetermined pressure on saidskin surface and whether at the same time said length axis of saidhousing is positioned substantially normal to said skin surface, thedistribution of said pressure over the area of said contact surfacebeing substantially uniform, said means for detecting enabling saidactuator means when the latter conditions are satisfied; and b) adisposable cartridge which contains a medication and which comprises apropellant and an igniter.
 15. A medication cartridge for a needlelesshypodermic injection system according to claim 14 for injecting a liquidmedication, said cartridge comprising a housing adapted to contain: a) afirst chamber containing a medication unit configured and dimensioned tostore a volume of liquid to be injected, said medication unit having afirst region and a second region that are in liquid communication witheach other, said first region being deformable and said second regionhaving an injection outlet, b) a second chamber containing a propellant,said first chamber being divided by an elastic barrier in two zones, afirst zone containing said medication unit and a second zone which is incommunication with said second chamber, so that upon ignition of thepropellant in the second chamber gas generated thereby expands into saidsecond zone of said first chamber, exerts pressure on and deforms saidbarrier which in turn transfers that pressure to and deforms saiddeformable first region of said medication unit and thereby causesejection of said medication through said injection outlet, and c) meansfor mechanically setting the volume available within said cartridge forgas expansion, so that said volume has a selected predetermined size.16. A medication cartridge according to claim 15, further comprising anenvelope which surrounds said elastic barrier and protects it fromdirect contact with hot gas generated by ignition of said propellant insaid second chamber.
 17. A medication cartridge according to claim 16,wherein said envelope also forms a gas seal between said housing andsaid medication unit containing said liquid medication.